This invention relates to a system of detecting whether or not electrical equipment is satisfactorily grounded (hereinafter referred to as "a non-grounding checking system"), which can be effectively applied to electrical equipment which should be grounded.
In general, electrical equipment has a grounding terminal for both security and stability of operation. Recently, electrical equipment has been employed in a variety of industrial fields, some of which require that the electrical equipment be especially positively grounded. Such electrical equipment is for instance ME (medical electronic) equipment, or equipment including a high voltage circuit. When electrical equipment of this type is used, the equipment has heretofore been grounded by connecting the housing of the electrical equipment to a grounding line, by inserting the plug of a power cord, which has a grounding line in addition to power supplying lines, into a receptacle provided on the power supply side so that the grounding line is connected to the grounding line which is provided on the power supply side. The electrical equipment can be operated after being grounded this way, but if the grounding line is broken or the grounding work for the receptacle on the power supply side is unsatisfactory, unexpected accidents could be caused. No effective countermeasure against this trouble has yet been provided.